• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.53-58
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• 2008

Film cooling effectiveness on a flat plate was measured with pressure sensitive paint. The pressure sensitive paint(PSP) changes the intensity of its emissive light with pressure and the characteristic was used in film cooling effectiveness measurement. The film coolants were air and nitrogen, and by comparing the intensity of PSP coated surface with each coolant, the film cooling effectiveness was calculated. Three blowing ratio of 0.5, 1, and 2 were tested with two mainstream turbulence intensities. Results clearly showed the effect of blowing ratio and mainstream turbulence intensity. As the blowing ratio increases, the film cooling effectiveness was decreased near the film cooling holes. However, the film cooling effectiveness far downstream from the injection hole was higher for higher blowing ratio. As the mainstream turbulence intensity increased, the film cooling effectiveness was decreased at far downstream from the injection hole.

• 한국자동차공학회논문집
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• 제24권6호
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• pp.619-626
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• 2016

The new 1.4 L turbocharged LPG direct injection (T-LPDI) engine is presented in this paper to improve the fuel efficiency of the vehicles installed with the 2.0 L LPG port fuel injection (LPI) engine, while maintaining the performance as a downsizing concept for the new engine platform development. Firstly, the return type high pressure LPG fuel supply system is designed and mounted in the new 1.4 L T-LPDI engine. As a result, this new engine shows a much better WOT performance and approximately 8 % of improved fuel economy level, as compared to the 2.0 L LPI vehicle. Secondly, the LPDI engine specific optimized design for high pressure fuel components and fuel injection control strategies are proposed and evaluated in order to overcome the restartability problem in a heat-soaked condition called the vapor lock phenomenon. Consequently, these experimental results illustrate a great potential for the developed 1.4 L T-LPDI engine as a possible substitute for the 2.0 L LPI engine.

• Applied Science and Convergence Technology
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• 제27권4호
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• pp.65-69
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• 2018

We studied the critical pressure characteristics of an anode type ion beam source driven by both charge repulsion and diffusion mechanism. The critical pressure $P_{crit}$ of the diffusion type ion beam source was linearly decreased from 2.5 mTorr to 0.5 mTorr when the gas injection was varied in 3~10 sccm, while the $P_{crit}$ of the charge repulsion ion beam source was remained at 3.5 mTorr. At the gas injection of 10 sccm, the range of having normal beam shape in the charge repulsion ion beam source was about 6.4 times wider than that in the diffusion type ion beam source. An impurity of Fe 2p (KE = 776.68 eV) of 12.88 at. % was observed from the glass surface treated with the abnormal beam of the charge repulsion type ion beam source. The body temperature of the diffusion type ion beam source was observed to increase rapidly at the rate of $1.9^{\circ}C/min$ for 30 minutes and to vary slowly at the rate of $0.1^{\circ}C/min$ for 200 minutes for an abnormal beam and normal beam, respectively.

• 한국소음진동공학회논문집
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• 제24권6호
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• pp.462-469
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• 2014

After drilling operations at the offshore plant, crude oil is producted under high pressure. After that time, oil recovery is reduced, because the pressure of the pipe inside is low during the secondary produce. At that time injection sea water at the pipe inside through water injection pump that the device increase to recovery. A variety of mathematical analysis during the detailed design analysis was not made through the dynamics characteristic at the domestic company. 2D model has reliability of analysis results for the uncomplicated model. Also element and the node the number of significantly less than in the 3D model. So, the temporal part is very effective. In addition, depending on the quality of mesh 3D is a real model and FEM model occurs error. So, user needs a lot of skill. In this paper, a 2D finite element analysis was performed through the dynamics analysis and the study model was validated.

• 대한환경공학회지
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• 제33권5호
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• pp.359-367
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• 2011

압력수 확산공정은 정수공정에서 응집제나 염소용해수를 고압의 압력수로 분사하여 혼합하는 공정이다. 본 연구의 목적은 압력수 확산공정에 대한 전산유체역학적(Computational Fluid Dynamics) 진단을 통해 투입한 약품의 완전 혼합거리 및 혼합 거리를 줄이기 위한 확산판의 크기와 설치거리를 도출하는 것이다. 진단결과 2,200 mm 대형관에 $5kg/cm^2$ 압력수를 50mm, 100 mm 분사관으로 분사할 경우 혼합이 완료되는 혼합거리는 4D였다. 혼합거리를 줄이기 위해 분사관 전방에 확산판을 설치할 경우 분사관이 50 mm일 때 0.1D 직경의 확산판을 분사관 전방 0.2D 거리에 설치하면 혼합거리를 3D로 줄일 수있다. 그러나 분사관이 100 mm인 경우는 확산판의 크기와 설치 거리와는 상관없이 확산판이 없는 4D보다 확산거리를 줄일 수 없는 것으로 진단되었다. 따라서 2,200 mm 관에 압력수를 분사하는 경우는 50 mm 분사관을 설치하는 것이 100 mm보다 훨씬 효율적인 것으로 나타났다.

• Design & Manufacturing
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• 제8권2호
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• pp.1-6
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• 2014

The narrow-pitched connectors are of interest for small-scale devices such as smart phones because of theirs caling. We conducted an injection molding analysis and a warp analysis for 0.3mm and 0.5mm pitch FPC connectors. We obtained a volumetric shrinkage of 4.344%, a clamping force of 0.2529 tonne, a maximum injection pressure of 76.3 MPa as optimized molding conditions for the 0.3mm pitch FPC connector. We found that, compared with the traditional injection molding technique, the injection molding for narrow-pitched connectors comes with distinct features like low clamping force, high injection molding pressure, and narrow gate size. Adding to the optimization analysis, the deflection of 0.5mm pitch FPC connector was analyzed as well. A maximum deflection of 0.053mm was calculated, which the actual deflection of 0.062mm was compared to. The results deduced a relative error of 17%. We conclude that the deflection analysis along with the optimization analysis can be used as an effective tool to predict the behavior of narrow-pitch connectors although the relative error may need to improve.

• Elastomers and Composites
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• 제47권4호
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• pp.347-354
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• 2012

사출성형에 CAE (Computer Aided Engineering)을 적용함으로써 사출 성형품 설계와 공정조절에 큰 도움이 된다. 또한 성형의 효율성을 최대화하고 개발기간의 단축, 그리고 고품질 제품을 확보하는데 도움이 크다. 특히 신제품 개발에 대한 설계방안을 제시하고 실패율을 감소시킬 수 있다. 현재 사출성형의 CAE는 2D는 물론 3D도 해석이 가능한데 이 두 가지 방식은 약간의 차이를 가짐에도 불구하고 해석 상 차이에 관한 비교 및 일반적인 가이드라인이 정해져 있지 않다. 본 연구에서는 제품의 두께, 형상 그리고 유한요소 수에 따른 2차원 해석과 3차원 해석을 비교하였다. 그리고 실험을 통해 얻은 캐비티 내의 압력과 온도를 해석결과와 비교하였다. 본 연구를 통하여 사출성형의 2D해석과 3D해석에 대한 가이드라인을 제시하고자 하였다.

• Tribology and Lubricants
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• 제32권6호
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• pp.183-188
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• 2016

Engine oil plays an important role in the mechanical lubrication and cooling of a vehicle engine. Recently, engine development has focused on the adoption of gasoline direct injection (GDI) and turbocharging methodology to achieve high-power and high-speed performance. However, oil dilution is a problem for GDI engines. Oil dilution occurs owing to high-pressure fuel injection into the combustion chamber when the engine is cold. The chemical components of engine oil are currently developed to accommodate gasoline fuel; however, bio-alcohol mixtures have become a recent trend in fuel development. Bio-alcohol fuels are alternatives to fossil fuels that can reduce vehicle emissions levels and greenhouse gas pollution. Therefore, the chemical components of engine oil should be improved to accommodate bio-alcohol fuels. This study employs a 2.0 L turbo-gas direct injection (T-GDI) engine in an experiment that dilutes oil with fuel. The experiment utilizes a variety of fuels, including sub-octane gasoline fuel (E0) and a bio-alcohol fuel mixture (Ethanol E3~E7). The results show that the lowest amount of oil dilution occurs when using E3 fuel. Analyzing the diluted engine oil by measuring density and moisture with respect to kinematic viscosity shows that the lowest values of these parameters occur when testing E3 fuel. The reason is confirmed to influence the vapor pressure of the low concentration bio-alcohol-fuel mixture.

• 소성∙가공
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• 제20권2호
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• pp.173-178
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• 2011

Environmental Stress Cracking(ESC) is one of the most common causes of unexpected brittle failure of thermoplastic polymers. The exposure of polymers to liquid chemicals tends to accelerate the crazing process, initiating crazes at stresses that are much lower than the stress causing crazing in air. In this study, ESC of acrylonitirile butadiene styrene(ABS) was investigated as a function of the molding conditions such as injection velocity, packing pressure, and melt temperature. A constant strain was applied to the injection molded specimens through a 1.26% strain jig and a mixture of toluene and isopropyl alcohol was used as the liquid chemical. In order to examine the effects of the molding conditions on ESC, an experimental design method was adopted and it was found that the injection velocity was the dominant factor. In addition, predictions from numerical analyses were compared with the experimental results. It was found that the residual stress in the injection molded part was associated with the environmental stress cracking resistance (ESCR).

• International Journal of Automotive Technology
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• 제2권3호
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• pp.93-101
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• 2001

Distribution of fuel-air mixture has a strong influence on performance and emissions of a compressed natural gas (CNG) engine. In this paper, parametric study is performed by KIVA-3V to investigate fuel-air mixture with respect to injection timing, cycle equivalence ratio and engine speed. With open-valve injection intensive mixing during intake and compression stroke results in relatively homogeneous mixture in the cylinder. Sequential induction of fuel-air mixture and fresh air results in stratification in the cylinder among the test cases at closed-valve injection. There is close similarity in the calculated distributions of the mixture in the cylinder with different cycle equivalence ratios and engine speeds. The results are compared against pressure traces and flame images obtained in a single cylinder engine converted from a 11L six-cylinder heavy duty diesel engine.